"Ellos hablan francés."
Translation:They speak French.
Yes, you are correct. "Ellos hablan francés" can be translated as They speak French or They are speaking French. For me, the choice depends on the context and what I am trying to emphasize. If someone asked me ¿Que lengua habla Julia? and you are not in the room, I would consider that to be "What language does Julia speak." If you are on the other side of the room and speaking with someone, I would consider that to be "What language is Julia speaking." Because there was no context here, I answered: "They speak French." With Duo, I always use the simplest answer unless it does not seem to fit..